1. Field of the Invention
The present invention relates to an apparatus for actuating or controlling the clamping jaws of a heavy-duty or power chuck disposed on a shop machine The clamping jaws are radially displaceably guided in a driven chuck body and are coupled via splined rods, keyways, levers, or similar connecting members with a rotatable or axially shiftable adjustment member. To produce a rotational adjustment movement, this adjustment member is drivingly connected with an actuator that is formed from a stationary reversible electric motor and a gear mechanism that is drivingly connected to the output side of the motor via a torque coupling.
2. Description of the Prior Art
German Offenlegungsschrift No. 15 52 302 Giraud et al dated Oct. 23, 1969 discloses an actuating apparatus of this general type. To produce the rotational movements that bring about the adjustment movements of the clamping jaws, this heretofore known apparatus is provided with a reduction gear mechanism in the form of a planetary-type differential gearing that is connected with the drive motor via a magnetic powder coupling. During normal extended operation of the turning machine, the drive motor is turned off and the drive pinion of the planetary-type differential gearing is uncoupled from this motor. However when a workpiece is being secured or removed, with the machine spindle stopped, the drive pinion is rotated by the drive motor, so that the clamping jaws can be appropriately adjusted via a helix.
Although during normal operation, with the coupling engaged, a readjustment movement of the clamping jaws could also be undertaken, in this operating state the drive motor must rotate in the same direction of rotation as does the machine spindle, and the adjustment member that is connected with the clamping jaws must be driven at a higher speed than is the machine spindle. The speed differentials between the two halves of the coupling are therefore extremely high with this known apparatus, and are no longer controllable.
It is therefore an object of the present invention to improve an apparatus of the aforementioned general type so that the drive motor of the actuator, in order to maintain the clamping force and at the same time undertake a retightening if needed, can constantly rotate at a constant speed and direction of rotation that are independent of the speed and rotation of the machine spindle, thereby always delivering a uniform torque. Furthermore, it should be possible to undertake the clamping and release of a workpiece by changing the direction of rotation of the actuator motor in a simple manner; it should also be possible to adjust the clamping force that acts upon the workpiece without difficulty. The capital investment necessary to realize this should be kept low, so that an economical manufacture and a compact construction can be realized.